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PCNSA Practice Question: Is troubleshooting a connectivity issue where…
A security engineer is troubleshooting a connectivity issue where internal users cannot reach a public web server hosted on the internet. The firewall is configured with a security policy that allows traffic from the internal zone to the external zone on port 80. The engineer notices that traffic is being dropped. Upon checking the session table, the engineer sees that the session is initiated correctly but the return traffic is not matching the existing session. What is the most likely cause?
⚠ Common exam trap
Candidates often confuse a NAT policy mismatch (which affects address translation) with a session state issue, but the key clue is that the session is initiated correctly—pointing to a routing asymmetry rather than a translation or policy problem.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Asymmetric routing
The session is initiated correctly, but return traffic is not matching the existing session. This is a classic symptom of asymmetric routing, where the forward traffic traverses one firewall and the return traffic takes a different path, bypassing the firewall that holds the session state. Palo Alto Networks firewalls are stateful and require both directions of traffic to pass through the same firewall to maintain session consistency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Application override configured for HTTP
Why it's wrong here
Application override would not cause session mismatch; it would force the application identification regardless of port.
- ✓
Asymmetric routing
Why this is correct
Asymmetric routing causes return traffic to take a different path, so the firewall does not see the return packets and cannot match them to the existing session.
- ✗
DNS resolution failure
Why it's wrong here
DNS resolution failure would prevent the user from resolving the server's IP address, but would not cause session mismatch for return traffic.
- ✗
NAT policy mismatch
Why it's wrong here
NAT policy mismatch would affect address translation but not the session lookup for return traffic.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSA practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSA exam.